Hawai'i is known for its active volcanoes, such as Kīlauea and Mauna Loa, which are part of the Hawaiian-Emperor seamount chain that extends for thousands of kilometers across the Pacific Ocean.
However, there is another volcano in this chain that is less well-known and less studied, because it is submerged under the sea.
This volcano is called Kama'ehuakanaloa, or Kama'ehu for short, and it is located about 32 km (20 miles) off the south coast of the Big Island of Hawai'i.
Kama'ehu is the youngest volcano in the Hawaiian-Emperor seamount chain, and it is still in its early stage of growth.
It is currently about 1,000 m (3,300 ft) below sea level, and it will take tens of thousands of years before it emerges above the water as a new island.
Kama'ehu is also the only active and exposed example of a pre-shield Hawaiian volcano, meaning that it has not yet reached the main stage of lava production that characterizes most Hawaiian volcanoes.
With that, scientists see Kama'ehu as an important natural laboratory for studying the origin and evolution of Hawaiian volcanoes, as well as their impact on the marine environment.
However, because of its remote and deep location, it is difficult to observe and monitor its activity. Until recently, the only confirmed eruption of Kama'ehu was the one that occurred in 1996, which was detected by a swarm of earthquakes on land.
Now, a new study led by researchers from the University of Hawai'i at Mānoa has revealed that Kama'ehu has erupted at least five times in the past 150 years, and possibly more.
How to date underwater eruptions
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The researchers used a combination of chemical analysis and underwater videos to estimate the ages of different lava flows on Kama'ehu, as per Phys.org.
They collected samples of quenched glassy lava from the seafloor using a submersible vehicle and measured the amount of radium-226 in each sample using a mass spectrometer.
Radium-226 is a radioactive isotope that decays at a known rate, and it is naturally present in magma. By comparing the amount of radium-226 in each sample with the amount expected in fresh magma, the researchers could infer how long ago the lava erupted.
The researchers also used video footage from submersible dives around Kama'ehu to identify different lava types and textures and to assess their degree of weathering and sedimentation.
These visual clues helped them to distinguish between older and younger lava flows, and to correlate them with their chemical ages.
The eruptive history of Kama'ehu
The results showed that Kama'ehu has erupted at least five times since 1870, with an average recurrence interval of about 30 years.
The most recent eruption was in 1996, which produced pillow lavas and lava tubes on the summit and upper flanks of the volcano, while previous eruptions were recorded in 1972, 1952, 1930, and 1870, which produced similar types of lava flows on different parts of the volcano.
The researchers also found evidence for eight older eruptions that occurred between 50 BC and AD 1700, with an average recurrence interval of about 200 years.
The study also revealed that Kama'ehu has a complex plumbing system that feeds magma from different sources and depths to different vents on the volcano.
The chemical composition and temperature of the magma varied between different eruptions and locations, indicating that Kama'ehu has multiple magma chambers and pathways beneath it.
The scientists also found that some eruptions were triggered by external factors, such as earthquakes or landslides, while others were driven by internal processes, such as magma accumulation or gas accumulation.
The implications and challenges of studying Kama'ehu
The study provides new insights into the growth and behavior of Kama'ehu, as well as its potential hazards and benefits, as per ScienceDaily.
Kama'ehu is an active volcano that can produce explosive eruptions that can generate large plumes of ash and gas, as well as submarine landslides that can cause tsunamis.
These events can pose risks to marine life, coastal communities, and maritime activities around Hawai'i.
On the other hand, Kama'ehu also creates new habitats for marine organisms, such as hydrothermal vents and coral reefs, which can support biodiversity and ecosystem services.
The study also highlights the challenges and opportunities of studying underwater volcanoes like Kama'ehu. Because they are inaccessible and unpredictable, they require advanced technologies and methods to observe and monitor them.
However, they also offer unique opportunities to explore the origin and evolution of volcanoes, as well as their interactions with the ocean and the biosphere.
Kama'ehu is a prime example of a hidden and mysterious volcano that can reveal secrets about the past, present, and future of Hawai'i and the Earth.
